How to properly light a scene that's both indoors and outdoors
On a bright sunny day, the exterior will always be much brighter than indoors by several magnitudes. In the real world, photographers deal with this by adding and hiding light sources and making the interiors brighter until they get an image with a dynamic range that is within the limitations of the imaging device and the artistic intentions they are after.

There is no reason why you couldn't do the same, with the added bonus that in 3D rendering you can create light suorces that are invisible to the camera... 

Create light sources the size of the windows and place them in a way that they don't block the incoming light, but suplement it. That way you'd still feel that the light is coming from outside the window, but in reality is coming from a light source inside the room. It is very important that you do not try to make the interiors as bright as the exteriors, it would break the illusion of realism. When you are indoors the exterior should feel a bit brighter and when looking at things from the outside the interior would be a somehow shaded (why would you want to buy a house that offers no escape from the intense sun light?)

A very important step towards realism is to create your scene with a much wider dynamic range, so that you can still keep values that are like those in the real world. But the trick is in how those values get displayed in the final image. The default sRGB color transforms for blender will severely limit the way light values can be displayed, try using the Filmic BLender transforms.